BBB make several different track pumps, topping out at £34.95. This is the cheapest in the range but it's pretty good.
The plastic construction makes it very light but the overall strength doesn't appear to suffer.
The dual-valve pump action is excellent and we had no problem inflating road tyres to their maximum 140psi, so it should be fine for all mountain bike rubber.
The base is less stable than most track pumps but at this price we're not complaining.